Beyond sex, gender, and other dilemmas: Human pelvic morphology from an integrative context

Recent research on the pelvis has clarified the flexibility of pelvic bones to manage nearly infinite possibilities in terms of selection and drift, while still maintaining excellent bipedalism. Despite this work, and the studies outlining the diversity of pelvic morphology across the hominin lineage, conversations continue to be stymied by distractions related to purported trade-offs that the different functions the pelvis must either allow for (e.g., parturition) or directly perform (e.g., attachment sites of muscles). Here we show that tight constraints on morphology are not evident in the pelvic variation of multiple human populations. We thus provide further evidence that human pelves are not geometrically similar and that pelvic morphology successfully balances the intersection of population history, active selective, and drift.

The Role of Biological Fusion and Anterior Column Support in a Long Lumbopelvic Spinal Fixation and Its Effect on the S1 Screw-An In Silico Biomechanics Analysis

STUDY DESIGN

Finite element analysis.

OBJECTIVE

The aim of this study was to determine the role of biological fusion and anterior column support in a long lumbopelvic spinal fixation.

SUMMARY OF BACKGROUND DATA

Retrospective studies have shown that adding anterior column support is not sensitive to construct failure, highlighting that posterior fusion quality may be a more important factor.

METHODS

Finite element models were created to match the average spinal-pelvic parameters of two patient cohorts reported in the literature: major failure and nonfailure. A moment load was applied at the T10 superior endplate to simulate gravimetric loading in a standing position. Effects of three factors on the biomechanical behavior of a fused spine were evaluated: sagittal alignment; posterior fusion versus no fusion; and anterior support at L4-S1 versus no anterior support.

RESULTS

Sagittal balance of the major failure group was positively correlated with 15% higher translation, 14% higher rotation, and 16% higher stress than in the nonfailure group. Simulated posterior fusion-only decreased motion by 32% and 29%, and alleviated rod stress by 15% and 5% and S1 screw stress by 26% and 35%, respectively, in major failure and non-failure groups. The addition of anterior fusion without posterior fusion did not help with rod stress alleviation but dramatically decreased S1 screw stress (by 57% and 41%), respectively. With both posterior fusion and anterior support, screw stress at the S1 was decreased by additional 30% and 6%, respectively.

CONCLUSION

The spinopelvic parameters of the major failure group produced increased gravity load, resulting in increased stresses in comparison to the nonfailure group. Simulated posterior "solid" fusion in the lumbar region helped reduce stresses in both major failure and nonfailure patients. Anterior column support was an important factor in reducing S1 screw stress, with or without posterior fusion, and should be considered for patients with poor alignment.Level of Evidence: N/A.

Sex-specific and age-specific characteristics of body composition and its effect on bone mineral density in adults in southern China: a cross-sectional study

OBJECTIVES

This study was an attempt to investigate the variation trend of body composition with ageing and explore the association between regional body composition and bone mineral density (BMD).

DESIGN

Cross-sectional study.

SETTING AND PARTICIPANTS

A total of 5749 healthy adults aged 20-95 years was recruited from 2004 to 2017.

PRIMARY OUTCOME MEASURES

Whole-body lean mass (LM), fat mass (FM), android FM, gynoid FM, appendicular lean mass (ALM) and BMD in the lumbar spine, femoral neck and total hip were obtained by dual-energy X-ray absorptiometry (DXA). The android/gynoid fat mass ratio (A/G FMR) based on DXA scan was calculated as an indicator of adipose distribution. Pearson correlation and multiple linear regression analyses were used to determine the associations between body composition, adipose distribution, and BMD of each skeletal site.

RESULTS

Whole-body FM, percentage of whole-body FM, Android FM and A/G FMR consistently increased with age in both genders, especially in women, and ALM began to decrease in the fifth decade for both men and women. In multivariable linear regression models with age, body mass index, A/G FMR and ALM as predictor variables, ALM was associated with the most BMD variance of all skeletal sites in men (standard β ranged from 0.207 to 0.405, p<0.001), although not the largest but still a positive predictor of BMD in women (standard β ranged from 0.074 to 0.186, p<0.05). A/G FMR was an inverse predictor of BMD at all skeletal sites for women (standard β ranged from -249 to -0.052, p<0.01) but not in men.

CONCLUSIONS

In this large cohort of Chinese adults, ALM had a strong positive association with BMD in both genders. A/G FMR as an indicator of central adipose accumulation was inversely associated with BMD in women but not in men.

Accuracy and Precision of an Ultrasound-Based Device to Measure the Pelvic Tilt in Several Positions

OBJECTIVES

A new ultrasound-based device is proposed to measure the patient-specific pelvic tilt in different daily positions. The aim of this study was to assess the accuracy of this device as well as the intraobserver and interobserver precisions.

METHODS

The accuracy was assessed by performing several tilt measurements with the device on a testing mechanical bench. The error was defined as the difference between the tilt measured with the device and the tilt provided by this test bench. Three physicians, a novice, an intermediate, and an expert user, were also asked to perform 10 measurements on 3 healthy volunteers with low, medium, and high body mass indices to analyze the intraobserver and interobserver precisions. These 10 measurements were performed in the standing, sitting, and supine positions.

RESULTS

The mean accuracy of the device ± SD was 1.1° ± 0.7° (range, 0°-4.0°). The interobserver and intraobserver precisions were excellent whatever the body mass index and good to excellent according to the positions. There was no learning curve, and the time required to complete the measurements was approximately 5 minutes.

CONCLUSIONS

This study presents an accurate and precise noninvasive device for measurement of the pelvic tilt in different positions.

Sex differences in bone density, geometry, and bone strength of competitive soccer players

OBJECTIVES

To examine sex differences in bone characteristics in competitive soccer players.

METHODS

43 soccer players (male, n=23; female, n=20), and 43 matched controls (males, n=23; females, n=20), completed the study. Areal BMD (aBMD) of the total body, lumbar spine, and dual femur and tibiae volumetric BMD (vBMD), bone geometry, and bone strength variables (pQCT) were measured. Bone-specific physical activity and training history were assessed.

RESULTS

Male soccer players had significantly greater (p≤0.05) total body and hip aBMD, hip strength indices and 4% and 38% tibia variables than females. Regression analyses determined that BFLBM, not sex, was the strongest predictor of bone variables. Female soccer players exhibited significantly greater percent differences from controls for tibiae variables than males (p≤0.05). Soccer players had greater aBMD and hip strength indices than controls (p≤0.040). Soccer-specific asymmetries were found for 38% total area (2.1%) and pSSI (3.8%), favoring the non-dominant leg (both p≤0.017).

CONCLUSION

Bone characteristics adjusted for body size were greater in male versus female soccer players. However, body composition variables were more important predictors of bone characteristics than sex. There were no sex differences in the magnitude of limb asymmetries, suggesting skeletal responsiveness to mechanical loading was similar in males and females.

Evolution of the human pelvis and obstructed labor: new explanations of an old obstetrical dilemma

Without cesarean delivery, obstructed labor can result in maternal and fetal injuries or even death given a disproportion in size between the fetus and the maternal birth canal. The precise frequency of obstructed labor is difficult to estimate because of the widespread use of cesarean delivery for indications other than proven cephalopelvic disproportion, but it has been estimated that at least 1 million mothers per year are affected by this disorder worldwide. Why is the fit between the fetus and the maternal pelvis so tight? Why did evolution not lead to a greater safety margin, as in other primates? Here we review current research and suggest new hypotheses on the evolution of human childbirth and pelvic morphology. In 1960, Washburn suggested that this obstetrical dilemma arose because the human pelvis is an evolutionary compromise between two functions, bipedal gait and childbirth. However, recent biomechanical and kinematic studies indicate that pelvic width does not considerably affect the efficiency of bipedal gait and thus is unlikely to have constrained the evolution of a wider birth canal. Instead, bipedalism may have primarily constrained the flexibility of the pubic symphysis during pregnancy, which opens much wider in most mammals with large fetuses than in humans. We argue that the birth canal is mainly constrained by the trade-off between 2 pregnancy-related functions: while a narrow pelvis is disadvantageous for childbirth, it offers better support for the weight exerted by the viscera and the large human fetus during the long gestation period. We discuss the implications of this hypothesis for understanding pelvic floor dysfunction. Furthermore, we propose that selection for a narrow pelvis has also acted in males because of the role of pelvic floor musculature in erectile function. Finally, we review the cliff-edge model of obstetric selection to explain why evolution cannot completely eliminate cephalopelvic disproportion. This model also predicts that the regular application of life-saving cesarean delivery has evolutionarily increased rates of cephalopelvic disproportion already. We address how evolutionary models contribute to understanding and decision making in obstetrics and gynecology as well as in devising health care policies.

Influence of musculotendon geometry variability in muscle forces and hip bone-on-bone forces during walking

Inverse dynamics problems are usually solved in the analysis of human gait to obtain reaction forces and moments at the joints. However, these actions are not the actual forces and moments supported by the joint structure, because they do not consider the forces of the muscles acting across the joint. Therefore, to analyse bone-on bone forces it is necessary to estimate those muscle forces. Usually, this problem is addressed by means of optimization algorithms. One of the parameters required to solve this problem is the musculotendon geometry. These data are usually taken from cadavers or MRI data from several subjects, different from the analysed subject. Then, the model is scaled to the subject morphology. This procedure constitutes a source of error. The goals of this work were two. First, to perform a sensitivity analysis of the influence of muscle insertion locations on the muscle forces acting on the hip joint and on the hip joint bone-on-bone forces. Second, to compare the hip joint bone-on-bone forces during gait cycle obtained through muscle insertion locations taken from a musculoskeletal model template and a scaling procedure to those obtained from a subject-specific model using an MRI of the subject. The problem was solved using OpenSim. Results showed that anatomical variability should be analysed from two perspectives. One the one hand, throughout the gait cycle, in a global way. On the other hand, at a characteristic instant of the gait cycle. Variations of ±1 cm in the position of the attachment points of certain muscles caused variations of up to 14.21% in averaged deviation of the muscle forces and 58.96% in the peak force in the modified muscle and variations up to 57.23% in the averaged deviation of the muscle force and up to 117.23% in the peak force in the rest of muscles. Then, the influence of that variability on muscle activity patterns and hip bone-on-bone forces could be described more precisely. A biomechanical analysis of a subject-specific musculoskeletal model was carried out. Using MRI data, variations up to 5 cm in the location of the insertion points were introduced. These modifications showed significant differences between the baseline model and the customized model: within the range [-12%, 10%] for muscle forces and around 35% of body weight for hip bone-on-bone forces.

Bone mineral density and estimated hip strength in men with anorexia nervosa, atypical anorexia nervosa and avoidant/restrictive food intake disorder

OBJECTIVE

Few bone mineral density (BMD) data are available in men with anorexia nervosa (AN), and none in those with atypical AN (ATYP) (AN psychological symptoms without low weight) or avoidant/restrictive food intake disorder (ARFID) (restrictive eating without AN psychological symptoms). We investigated the prevalence and determinants of low BMD and estimated hip strength in men with these disorders.

DESIGN

Cross-sectional: two centres.

PATIENTS

A total of 103 men, 18-63 years: AN (n = 26), ARFID (n = 11), ATYP (n = 18), healthy controls (HC) (n = 48).

MEASUREMENTS

Body composition, BMD and estimated hip strength (section modulus and buckling ratio) by DXA (Hologic). Serum 25OH vitamin D was quantified, as was daily calcium intake in a subset of subjects.

RESULTS

Mean BMI was lowest in AN and ARFID, higher in ATYP and highest in HC (AN 14.7 ± 1.8, ARFID 15.3 ± 1.5, ATYP 20.6 ± 2.0, HC 23.7 ± 3.3 kg/m² ) (P < 0.0005). Mean BMD Z-scores at spine and hip were lower in AN and ARFID, but not ATYP, than HC (postero-anterior (PA) spine AN -2.05 ± 1.58, ARFID -1.33 ± 1.21, ATYP -0.59 ± 1.77, HC -0.12 ± 1.17) (P < 0.05). 65% AN, 18% ARFID, 33% ATYP and 6% HC had BMD Z-scores <-2 at ≥1 site (AN and ATYP vs HC, P < 0.01). Mean section modulus Z-scores were lower in AN than HC (P < 0.01). Lower BMI, muscle mass and vitamin D levels (R = 0.33-0.64), as well as longer disease duration (R = -0.51 to -0.58), were associated with lower BMD (P < 0.05).

CONCLUSIONS

Men with AN, ARFID and ATYP are at risk for low BMD. Men with these eating disorders who are low weight, or who have low muscle mass, long illness duration and/or vitamin D deficiency, may be at particularly high risk.

Quantifying the force transmission through the pelvic joints during total hip arthroplasty: A pilot cadaveric study

BACKGROUND

Total hip arthroplasty is one of the most successful and cost effective procedures in orthopedics. The purpose of this study is to investigate force transmission through the sacroiliac joint as a possible source of post-operative pain after total hip arthroplasty through the following three questions: Does the ipsilateral sacroiliac joint, contralateral sacroiliac joint, or pubic symphysis experience more force during placement? Does the larger mallet used to seat the implant generate a higher force? Does the specimen's bone density or BMI alter force transmission?

METHODS

A solid design acetabular component was impacted into five human cadaver pelves with intact soft tissues. The pressure at both sacroiliac joints and the pubic symphysis was measured during cup placement. This same procedure was replicated using an existing pelvis finite element model to use for comparison.

FINDINGS

The location of the peak force for each hammer strike was found to be specimen specific. The finite model results indicated the ipsilateral sacroiliac joint had the highest pressure and strain followed by the pubic symphysis over the course of the full simulation. The heft of the mallet and bone mineral density did not predict force values or locations. The largest median force was generated in extremely obese specimens.

INTERPRETATION

Contrary to previous ideas, it is highly unlikely that forces experienced at the pelvic joints are large enough to contribute post-operative pain during impaction of an acetabular component. These results indicate more force is conveyed to the pubic symphysis compared to the sacroiliac joints.

The relationship between objectively assessed physical activity and bone health in older adults differs by sex and is mediated by lean mass

Relationships between objectively assessed free-living physical activity (PA) and changes in bone health over time are poorly understood in older adults. This study suggests these relationships are sex-specific and that body composition may influence the mechanical loading benefits of PA.

INTRODUCTION

To investigate associations of objectively assessed PA and bone health in community-dwelling older adults.

METHODS

This secondary analysis of a subset of the Tasmanian Older Adult Cohort study included participants with PA assessed utilising ActiGraph GT1M accelerometers over 7 days (N = 209 participants, 53% female; mean ± SD age 64.5 ± 7.2 years). Steps/day and PA intensity were estimated via established thresholds. Bone mineral content (BMC) was acquired at the total hip, lumbar spine, legs and whole body by DXA at baseline and approximately 2.2 years later. Relationships between PA and BMC were assessed by multivariable linear regression analyses adjusted for age, smoking status, height and total lean mass.

RESULTS

Men with above-median total hip BMC completed significantly less steps per day, but there was no significant difference in PA intensity compared with those with below-median BMC. There were no significant differences in PA in women stratified by median BMC. In women, steps/day were positively associated with leg BMC (B = 0.178; P = 0.017), and sedentary behaviour was negatively associated with leg BMC (- 0.165; 0.016) at baseline. After adjustment for confounders including lean mass and height, higher sedentary behaviour at baseline was associated with declines in femoral neck BMC (- 0.286; 0.011) but also with increases in pelvic BMC (0.246; 0.030) in men and increases in total hip BMC (0.215; 0.032) in women, over 2.2 years. No other significant longitudinal associations were observed after adjustment for body composition.

CONCLUSIONS

Associations of accelerometer-determined sedentary behaviour and PA with bone health in older adults differ by sex and anatomical site and are mediated by body composition.

Are There Age- and Sex-related Differences in Spinal Sagittal Alignment and Balance Among Taiwanese Asymptomatic Adults?

BACKGROUND

Sagittal spinopelvic balance and proper sagittal alignment are important when planning corrective or reconstructive spinal surgery. Prior research suggests that people from different races and countries have moderate divergence; to the best of our knowledge, the population of Taiwan has not been studied with respect to this parameter.

QUESTIONS/PURPOSES

To investigate normal age- and sex-related differences in whole-spine sagittal alignment and balance of asymptomatic adults without spinal disorders.

METHODS

In this prospective study, we used convenience sampling to recruit asymptomatic volunteers who accompanied patients in the outpatient orthopaedic department. One hundred forty males with a mean age of 48 ± 19 years and 252 females with a mean age of 53 ± 17 years underwent standing lateral radiographs of the whole spine. For analysis, participants were divided in three groups by age (20 to 40 years, 41 to 60 years, and 61 to 80 years) and analyzed by sex (male and female). The following eight radiologic parameters were measured: sacral slope, pelvic tilt, pelvic incidence, thoracic kyphosis, lumbar lordosis, cervical lordosis, C2-C7 sagittal vertical axis, and C7-S1 sagittal vertical axis. Three observers performed estimations of the sagittal parameters twice, and the intraclass correlation coefficients for inter- and intraobserver variability were 0.81 and 0.83.

RESULTS

The mean pelvic incidence was 49° ± 12°; lumbar lordosis was smaller in the group that was 61 to 80 years old than in the groups that were 20 to 40 years and 41 to 60 years (95% CI of the difference, 4.50-13.64 and 1.00- 9.60; p < 0.001), while cervical lordosis was greater in the 61 to 80 years age group than the other two groups (95% CI of the difference, -14.64 to -6.57 and -11.57 to -3.45; p < 0.001). The mean C7-S1 sagittal vertical axis was 30 ± 29 mm, and there was no difference among the three groups and between males and females. Pelvic tilt was greater in the group 61 to 80 years old than the 20 to 40 years and 41 to 60 years age groups (95% CI of the difference, -10.81 to -5.42 and -7.15 to -2.08; p < 0.001), while sacral slope was larger in 61 to 80 years age group than in the 41 to 60 years group (95% CI of the difference, 0.79-6.25; p = 0.006). C7 slope was greater in 61 to 80 years age group than in the 20 to 40 years group (95% CI of the difference, -7.49 to -1.26; p = 0.002) and larger in 41 to 60 years age group than in 20 to 40 years group (95% CI of the difference, -6.31 to -0.05; p = 0.045). C2-C7 sagittal vertical axis was greater in males than in females (95% CI of the difference, 2.84-7.74; p < 0.001). C7 slope was negatively correlated with thoracic kyphosis (95% CI of the difference, -0.619 to 0.468; p < 0.001) and lumbar lordosis (95% CI of the difference, -0.356 to -0.223; p < 0.001), and positively correlated with pelvic incidence (95% CI of the difference, 0.058- 0.215; p < 0.001) and cervical lordosis (95% CI of the difference, 0.228 - 0.334; p < 0.001).

CONCLUSIONS

Normal values of the spinopelvic sagittal parameters vary by age and sex in Taiwanese individuals.

CLINICAL RELEVANCE

Pelvic incidence and sacral slope observed in this population seemed smaller than those reported in other studies of white populations; this seems important when considering spine surgery in Taiwanese patients. Future studies should include collection of whole body sagittal parameters of larger and more-diverse populations, and assessments of patients with symptomatic spinal disorders.

Effect of parity on bone mineral density: A systematic review and meta-analysis

INTRODUCTION

Parity has been suggested as a possible factor affecting bone health in women. However, study results on its association with bone mineral density are conflicting.

METHODS

PubMed, EMBASE, the Cochrane Library, and Korean online databases were searched using the terms "parity" and "bone mineral density", in May 2016. Two independent reviewers extracted the mean and standard deviation of bone mineral density measurements of the femoral neck, spine, and total hip in nulliparous and parous healthy women.

RESULTS

Among the initial 10,146 studies, 10 articles comprising 24,771 women met the inclusion criteria. The overall effect of parity on bone mineral density was positive (mean difference=5.97mg/cm²; 95% CI 2.37 to 9.57; P=0.001). The effect appears site-specific as parity was not significantly associated with the bone mineral density of the femoral neck (P=0.09) and lumbar spine (P=0.17), but parous women had significantly higher bone mineral density of the total hip compared to nulliparous women (mean difference=5.98mg/cm²; 95% CI 1.72 to 10.24; P=0.006). No obvious heterogeneity existed among the included studies (femoral neck I²=0%; spine I²=31%; total hip I²=0%).

CONCLUSION

Parity has a positive effect on bone in healthy, community-dwelling women and its effect appears site-specific.

Sagittal lumbo-pelvic alignment in the sitting position of elderly persons

INTRODUCTION

In elderly persons, the sitting position in daily life is very important due to the weakness in locomotion. In previous studies, sagittal spinal alignment was mainly analyzed in the standing position. However, in order to study the sagittal spinal alignment of elderly persons, the estimation of spinal alignment in the sitting posture is also important. We proposed that there is a characteristic spinal alignment in elderly persons in the sitting position. The purpose of this study was to evaluate the sagittal lumbo-pelvic alignment in the standing and sitting positions in elderly persons.

SUBJECTS & METHODS

This study included 73 young adult subjects (48 men and 25 women; age 34.4 ± 8.1 years) and 107 elderly subjects (65 men and 42 women; age 67.6 ± 8.3 years). The following radiographic parameters were determined by computer-assisted measurement: L1L5 angle (L1L5), lumbosacral angle (LSA), sacral slope (SS), pelvic tilt (PT), and pelvic incidence (PI).

RESULTS

L1L5 decreased and the pelvis rotated posteriorly in the sitting position in both young adults and elderly persons. However, the extent of alignment difference between standing and sitting in elderly persons was nearly half that of young adults (in particular, the lumbo-pelvic junction, LSA, was smaller). Regarding the extent of correlation between aging and lumbo-pelvic alignment parameters, there were significant correlations. In elderly persons, the correlation between L1L5 and PT had a tendency to be poor in the sitting position.

CONCLUSION

The elderly in the sitting position showed greater lumbar lordosis and higher sacral slope than in young adults, and the correlations among lumbo-pelvic parameters were poorer than those of young adults. Thus, when moving from sitting to standing, the lumbo-pelvic mobility in the sagittal plane is suspected to be poor in elderly persons.

Effect of Abaloparatide vs Placebo on New Vertebral Fractures in Postmenopausal Women With Osteoporosis: A Randomized Clinical Trial

IMPORTANCE

Additional therapies are needed for prevention of osteoporotic fractures. Abaloparatide is a selective activator of the parathyroid hormone type 1 receptor.

OBJECTIVE

To determine the efficacy and safety of abaloparatide, 80 μg, vs placebo for prevention of new vertebral fracture in postmenopausal women at risk of osteoporotic fracture.

DESIGN, SETTING, AND PARTICIPANTS

The Abaloparatide Comparator Trial In Vertebral Endpoints (ACTIVE) was a phase 3, double-blind, RCT (March 2011-October 2014) at 28 sites in 10 countries. Postmenopausal women with bone mineral density (BMD) T score ≤-2.5 and >-5.0 at the lumbar spine or femoral neck and radiological evidence ≥2 mild or ≥1 moderate lumbar or thoracic vertebral fracture or history of low-trauma nonvertebral fracture within the past 5 years were eligible. Postmenopausal women (>65 y) with fracture criteria and a T score ≤-2.0 and >-5.0 or without fracture criteria and a T score ≤-3.0 and >-5.0 could enroll.

INTERVENTIONS

Blinded, daily subcutaneous injections of placebo (n = 821); abaloparatide, 80 μg (n = 824); or open-label teriparatide, 20 μg (n = 818) for 18 months.

MAIN OUTCOMES AND MEASURES

Primary end point was percentage of participants with new vertebral fracture in the abaloparatide vs placebo groups. Sample size was set to detect a 4% difference (57% risk reduction) between treatment groups. Secondary end points included change in BMD at total hip, femoral neck, and lumbar spine in abaloparatide-treated vs placebo participants and time to first incident nonvertebral fracture. Hypercalcemia was a prespecified safety end point in abaloparatide-treated vs teriparatide participants.

RESULTS

Among 2463 women (mean age, 69 years [range, 49-86]), 1901 completed the study. New morphometric vertebral fractures occurred less frequently in the active treatment groups vs placebo. The Kaplan-Meier estimated event rate for nonvertebral fracture was lower with abaloparatide vs placebo. BMD increases were greater with abaloparatide than placebo (all P < .001). Incidence of hypercalcemia was lower with abaloparatide (3.4%) vs teriparatide (6.4%) (risk difference [RD], −2.96 [95%CI, −5.12 to −0.87]; P = .006). [table: see text].

CONCLUSIONS AND RELEVANCE

Among postmenopausal women with osteoporosis, the use of subcutaneous abaloparatide, compared with placebo, reduced the risk of new vertebral and nonvertebral fractures over 18 months. Further research is needed to understand the clinical importance of RD, the risks and benefits of abaloparatide treatment, and the efficacy of abaloparatide vs other osteoporosis treatments.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01343004.

Normative values of spino-pelvic sagittal alignment, balance, age, and health-related quality of life in a cohort of healthy adult subjects

PURPOSE

To elucidate the normative values of whole body sagittal alignment and balance of a healthy population in the standing position; and to clarify the relationship among the alignment, balance, health-related quality of life (HRQOL), and age.

METHODS

Healthy Japanese adult volunteers [n = 126, mean age 39.4 years (20-69), M/F = 30/96] with no history of spinal disease were enrolled in a cross-sectional cohort study. The Oswestry Disability Index (ODI) questionnaire was administered and subjects were scanned from the center of the acoustic meati (CAM) to the feet while standing on a force plate to determine the gravity line (GL), and the distance between CAM and GL (CAM-GL) was measured in the sagittal plane. Standard X-ray parameters were measured from the head to the lower extremities. ODI was compared among age groups stratified by decade. Correlations were investigated by simple linear regression analysis. Ideal lumbar lordosis was investigated using the least squares method.

RESULTS

The present study yielded normative values for whole standing sagittal alignment including head and lower extremities in a cohort of 126 healthy adult volunteers, comparable to previous reports and thus a formula for ideal lumbar lordosis was deduced: LL = 32.9 + 0.60 × PI - 0.23 × age. There was a tendency of positive correlation between McGregor slope, thoracic kyphosis, PT, and age. SVA, T1 pelvic angle, sacrofemoral angle, knee flexion angle, and ankle flexion angle, but not CAM-GL, increased with age, suggesting that the spinopelvic alignment changes with age, but standing whole body alignment is compensated for to preserve a horizontal gaze. ODI tended to increase from the 40s in the domain of pain intensity, personal care, traveling, and total score. ODI weakly, but significantly positively correlated with age and PI-LL.

CONCLUSION

Whole body standing alignment even in healthy subjects gradually deteriorates with age, but is compensated to preserve a horizontal gaze. HRQOL is also affected by aging and spinopelvic malalignment.

Orthodontic mini-implant stability at different insertion depths : Sensitivity of three stability measurement methods

OBJECTIVES

The purpose of this work was to evaluate the influence of insertion depth on the stability of orthodontic mini-implants. Sensitivity of three different methods to measure implant stability based on differences in insertion depth were determined.

METHODS

A total of 82 mini-implants (2 × 9 mm) were inserted into pelvic bone of Swabian Hall pigs. Each implant was inserted stepwise to depths of 4, 5, 6, 7, and 8 mm. At each of these depths, three different methods were used to measure implant stability, including maximum insertion torque (MIT), resonance frequency analysis (RFA), and Periotest(®). Differences between the recorded values were statistically analyzed and the methods tested for correlations.

RESULTS

Almost linear changes from each insertion depth were measured with the values of RFA [implant stability quotient (ISQ) values range from 1-100], which increased from 6.95 ± 2.85 ISQ at 4 mm to 34.63 ± 5.51 ISQ at 8 mm, and with those of Periotest(®) [periotest values (PTV) range from -8 to 50], which decreased from 13.24 ± 4.03 PTV to -2.89 ± 1.87 PTV. Both methods were found to record highly significant (p < 0.0001) changes for each additional millimeter of insertion depth. The MIT increased significantly (p < 0.0001) from 153.67 ± 69.32 Nmm to 261 ± 103.73 Nmm between 4 and 5 mm of insertion depth but no further significant changes were observed as the implants were driven deeper. The RFA and Periotest(®) values were highly correlated (r = -0.907).

CONCLUSIONS

Mini-implant stability varies significantly with insertion depth. The RFA and the Periotest(®) yielded a linear relationship between stability and insertion depth. MIT does not appear to be an adequate method to determine implant stability based on insertion depth.

Contributions of fat mass and fat distribution to hip bone strength in healthy postmenopausal Chinese women

The fat and bone connection is complicated, and the effect of adipose tissue on hip bone strength remains unclear. The aim of this study was to clarify the relative contribution of body fat accumulation and fat distribution to the determination of proximal femur strength in healthy postmenopausal Chinese women. This cross-sectional study enrolled 528 healthy postmenopausal women without medication history or known diseases. Total lean mass (LM), appendicular LM (ALM), percentage of lean mass (PLM), total fat mass (FM), appendicular FM (AFM), percentage of body fat (PBF), android and gynoid fat amount, android-to-gynoid fat ratio (AOI), bone mineral density (BMD), and proximal femur geometry were measured by dual energy X-ray absorptiometry. Hip structure analysis was used to compute some variables as geometric strength-related parameters by analyzing the images of the hip generated from DXA scans. Correlation analyses among anthropometrics, variables of body composition and bone mass, and geometric indices of hip bone strength were performed with stepwise linear regression analyses as well as Pearson's correlation analysis. In univariate analysis, there were significantly inverse correlations between age, years since menopause (YSM), hip BMD, and hip geometric parameters. Bone data were positively related to height, body weight, LM, ALM, FM, AFM, and PBF but negatively related to AOI and amount of android fat (all P < 0.05). AFM and AOI were significantly related to most anthropometric parameters. AFM was positively associated with height, body weight, and BMI. AFM was negatively associated with age and YSM. AOI was negatively associated with height, body weight, and BMI. AOI positively associated with age and YSM. LM, ALM, and FM had a positive relationship with anthropometric parameters (P < 0.05 for all). PLM had a negative relationship with those parameters. The correlation between LM, ALM, FM, PLM, ALM, age, and YSM was not significant. In multivariate linear regression analysis, the hip bone strength was observed to have a consistent and unchanged positive association with AFM and a negative association with AOI, whereas its association with other variables of body composition was not significant after adjusting for age, years since menopause, height, body weight, and BMI. AFM may be a positively protective effect for hip bone strength while AOI, rather than android fat, shows a strong negative association with hip bone strength after making an adjustment for confounders (age, YSM, height, body weight, and BMI) in healthy postmenopausal Chinese women. Rational weight control and AOI reduction during menopause may have vital clinical significance in decreasing postmenopausal osteoporosis.

Geometric parameterisation of pelvic bone and cartilage in contact analysis of the natural hip: an initial study

Parameterised finite element models of the human hip have the potential to allow controlled analysis of the effect of individual geometric features on the contact mechanics of the joint. However, the challenge lies in defining a set of parameters which sufficiently capture the joint geometry in order to distinguish between individuals. In this study, a simple set of parameters to describe the geometries of acetabulum and cartilage in the hip were extracted from two segmentation-based models, which were then used to generate the parameterised finite element models for the two subjects. The contact pressure and contact area at the articular surface predicted from the parameterised finite element models were compared with the results from the segmentation-based models. The differences in the predicted results between the parameterised models and segmentation-based models were found to be within 11% across seven activities simulated. In addition, the parameterised models were able to replicate features of the contact pressure/area fluctuations over the loading cycle that differed between the two subjects. These results provide confidence that the parameterised approach could be used to generate representative finite element models of the human hip for contact analysis. Such a method has the potential to be used to systematically evaluate geometric features that can be captured from simple clinical measurements and provide a cost- and time-effective approach for stratification of the acetabular geometries in the patient population.

Lean Mass Appears to Be More Strongly Associated with Bone Health than Fat Mass in Urban Black South African Women

OBJECTIVES

To examine the association between body composition (fat mass, lean mass and body mass index, BMI) and bone health (bone mineral density, BMD and fracture risk) in urban black South African women.

DESIGN

A cross sectional study examining associations between body composition, dietary intake (food frequency questionnaire), habitual physical activity (Activity energy expenditure (AEE) measured using an accelerometer with combined heart rate monitor and physical activity questionnaire) and bone health (BMD using dual-energy X ray absorptiometry, DXA and fracture risk).

SETTING

Urban community dwellers from Ikageng in the North-West Province of South Africa.

PARTICIPANTS

One hundred and eighty nine (189) healthy postmenopausal women aged ≥43 years.

RESULTS

Fat mass and lean mass were significantly associated with BMD and fracture risk when adjusted for potential confounders. However, lean mass and not fat mass remained significantly associated with femoral neck BMD (β = 0.49, p <0.001), spine BMD (β = 0.48, p< 0.0001) and hip BMD (β = 0.59, p< 0.0001). Lean mass was also negatively associated with fracture risk (β = -0.19 p =0.04) when both lean and fat mass were in the same model.

CONCLUSION

Lean mass and fat mass were positively associated with femoral neck, spine and hip BMDs and negatively associated with fracture risk in urban black South African women. Our finding suggests that increasing lean mass rather than fat mass is beneficial to bone health. Our study emphasises the importance of positive lifestyle changes, intake of calcium from dairy and adequate weight to maintain and improve bone health of postmenopausal women.

Differential skeletal impact of tenofovir disoproxil fumarate in young versus old HIV-infected adults

BACKGROUND

Lower peak bone mass in early adulthood predicts subsequent fragility fractures. Antiretroviral toxicity could contribute to young HIV-infected individuals not achieving adequate peak bone mass.

OBJECTIVE

To determine if tenofovir disoproxil fumarate's (TDF) effect on bone mineral density (BMD) differs by age.

METHODS

We examined BMD data at the lumbar spine and hip from AIDS Clinical Trials Group (ACTG) A5224s and ASSERT and randomized treatment-naive studies comparing TDF/emtricitabine versus abacavir/lamivudine (with efavirenz or atazanavir/ritonavir). In this post hoc analysis, we defined the TDF effect as the difference between mean 48-week BMD per cent changes for lumbar spine and hip in individuals randomized to TDF versus abacavir. We used multivariable linear regression to compare the TDF effect in individuals younger and older than 30 years. If TDF effect by age did not differ significantly between studies, we pooled study populations. Otherwise, analyses were conducted separately within each study population.

RESULTS

Among 652 subjects, 21% were below age 30 years. The relationship between age and TDF effect significantly differed between A5224s and ASSERT (P = 0.008 for lumbar spine; P = 0.007 for hip). In A5224s, there was more bone loss with TDF at lumbar spine and hip in subjects under 30 years old versus in older subjects ( - 4.5% vs - 1.4%; P = 0.045; - 4.3% vs - 1.6%; P = 0.026, respectively). There was no significant evidence for this age-associated TDF effect in ASSERT.

CONCLUSIONS

There was heterogeneity in the observed effect of TDF on bone density in young adults compared to older adults, suggesting that further investigation is required to understand the impact of age on BMD decline with TDF.

Two-leg alternate loading model--a different approach to biomechanical investigations of fixation methods of the injured pelvic ring with focus on the pubic symphysis

The dorsal component of the pelvic ring is considered to be the most essential element for the stability of the pelvic ring. None of the current biomechanical set-ups include the effect of shear stresses by alternating loads that the pelvic ring has to withstand during walking. We hypothesize that a biomechanical test set-up with two-leg alternate loading will lead to stress imitation at the pubic symphysis that are more similar to existing strains than other test set-ups, and would, therefore, be more adequate for biomechanical testing of fixation methods. A new biomechanical two-leg standing test set-up with an alternate pelvic loading was constructed and was validated with six human pelvises from fresh frozen cadavers. Three-dimensional motion tracking was performed. The specimens were subjected to a non-destructive quasi-static test and a non-destructive cyclic test with progressive load amplitude from 170 N to 340 N over 1000 cycles. The initial rotational 'range of motion' and 'mean displacement' around the vertical axis for a pre-load of 170 N was about 0.3° and 0.2°, respectively, increasing by 0.1-0.2° at a load of 340 N. The rotation around the vertical axis and the translation along the frontal horizontal axis confirmed the stability of the pubic symphysis. The rate of ascend of displacements decreased, once the rotation reached 1° or the translation reached 1mm. The current biomechanical test set-up was compared with previous clinical findings, and the method was found valid for measuring inter-segmentary movements at the pubic symphysis.

Runx-2 gene expression is associated with age-related changes of bone mineral density in the healthy young-adult population

Bone mineral density (BMD) and peak bone mass (PBM) are important determinants of skeletal resistance. The development of bone densitometry improved the possibility of studying BMD and the influence of genetic and environmental factors on bone. Heredity factors are important for BMD, and Runx-2 is accepted as a regulator of osteoblasts and bone formation. The aim of our study was to evaluate the behavior of Runx-2 during skeletal maturity in the healthy young-adult population. We analyzed spine and hip BMD in 153 volunteers, 98 women and 55 men, using dual-energy X-ray absorptiometry. In a subgroup of these volunteers, a sample of peripheral blood was taken to perform gene expression analysis of Runx-2 both in peripheral mesenchymal stem cells (MSCs; 28 subjects) and in peripheral mononuclear cells (PBMCs; 140 subjects). In our work BMD was comparable in both genders after puberty, then became higher in men than women during the third and fourth decades. PBM was achieved in the third decade in women and in the fourth in men. More interestingly, Runx-2 gene expression highly correlated with BMD in both genders. MSCs and PBMCs showed the same gene expression profile of Runx-2. In conclusion, PBM is reached earlier in females, BMD becomes higher in males later in life, and BMD and PBM are strictly associated with Runx-2. In addition, PBMC should be considered an important source for gene expression analysis in bone diseases.

Evaluation of pelvis slope and flattening on children gymnasts by Biophotogrammetry technique

This work proposes to detect possible affections or abnormalities in pelvic belt region in a group of rhythmic gymnastics due to the need for studies in the field of biomechanics and structural evaluation of human being. The methodology for this study used a tool called Biophotogrammetry. This technique has analyzed, through scanned images, the structural pelvic girdle bone profile of 64 practitioners of rhythmic gymnastics. The results of this study have presented weighted averages of 45.07±9.78° between the right pelvic slope (RPS) and left pelvic slope (LPS) and 91.74±2.50° for flattening of the pelvis (FP). Therefore, it is concluded that the Biophotogrammetry technique provides data related to the gold standard radiography test, used as reference for the pelvic girdle measurements.

[Sagittal balance of the spine: a therapeutic revolution]

In humans, the erect position and bipedal walk is possible because of a balance between pelvic and spinal parameters. The most important pelvic parameter is the pelvic incidence which represents the base on which the spine lies. With aging, thoracic kyphosis increases, lumbar lordosis decreases, compromising the spino-pelvic balance. Compensatory phenomenons are possible, but rely mostly on the amplitude of pelvic incidence. Analysis of spino-pelvic parameters and detection of a compensated or uncompensated sagittal imbalance are mandatory before any therapeutic action is undertaken for a degenerative pathology of the spine.

Bone mineral density discordance and exploration of one of its causes

Discordances between hip and spine areal density T-score values are common and incompletely understood. In a cohort of 1157 postmenopausal women, discordances of greater than 10% occurred in 91%, with spine bone mineral density (BMD) T-scores significantly less negative than femoral neck (FN) T-scores (p<0.001). However, when T-scores based on bone mineral content (BMC) rather than BMD were used, the mean discordance was not significantly different from 0. This was largely because BMC at the FN had seemingly declined with age less rapidly than had BMD at that site. This can be explained by age-related areal expansion at the hip, which would be missed in the reported BMD output. One consequence is that if BMC-based T-scores are used to classify patients, substantially fewer individuals would have been judged osteoporotic in this cohort (two-thirds fewer for spine and three-fourths fewer for hip).

Re-ossification of the pelvis following hemipelvectomy for trauma

We present a patient who underwent delayed sub-periosteal hemipelvectomy for control of infection and to enable soft-tissue cover after trauma. At four months after amputation, clinical examination and radiographs demonstrated almost complete re-ossification of the hemipelvis. This has allowed the patient to regain sitting balance and to use a walking prosthesis designed for patients following disarticulation of the hip. After 14 months from injury, no perineal hernia has developed, and no dysfunction of pelvic organs is attributable to heterotopic bone formation or adhesions. The patient's mobility with a prosthesis is similar to that expected of a through-hip amputee.

Development and testing of a more realistic pelvis for the Hybrid III 6-year-old ATD

OBJECTIVE

Design and test a new pelvis for the Hybrid III 6-year-old (6YO) anthropometric test device (ATD) with a more humanlike bone structure, flesh contour, and flesh stiffness intended to provide more realistic interaction with belt restraints.

METHODS

Target geometry for the new pelvis bone was based on a 3D model of the skeletal pelvis derived from statistical analysis of pediatric computed tomography (CT) scans. The current pelvis bone was reshaped to better match the target geometry, with a particular emphasis on the contour in the areas of belt interaction. The prominence representing the anterior-superior iliac spine (ASIS) was lowered by 15 mm. The pelvis flesh was molded using softer vinyl while maintaining a 10-mm flesh margin over the ASIS. A series of 20 sled tests was conducted to compare the performance of the modified pelvis with the current Hybrid III pelvis.

RESULTS

In a series of sled tests using a range of belt anchorage locations, a dummy equipped with the new pelvis did not submarine in conditions where the lap belt was positioned below the ASIS. Tests run with the lap belt initially positioned over the ASIS resulted in submarining, unlike tests performed with the standard dummy pelvis.

CONCLUSIONS

The new pelvis for the 6YO Hybrid III ATD better represents the skeletal and flesh geometry of similar-sized children. The ATD equipped with the new pelvis is more sensitive to lap belt geometry than the standard ATD. The modified ATD may provide an improved assessment of booster seats and belt restraints intended for child occupants.

[Finite element analysis for modular hemipelvic endoprosthesis during loaded gait cycle]

OBJECTIVE

To analyze the biomechanical characteristics of modular hemipelvic endoprosthesis in gait cycle using finite element analysis method, and the effect of pubic connection plate on stress distribution.

METHODS

Three dimensional finite element model of periacetabular defect reconstructed with modular hemipelvic endoprosthesis was established. The hip contact forces, which were published from Free University of Berlin, under gait cycle were applied in the load of Abaqus 6.7. Then the simulation was conducted and four characteristic time points were identified, 17%, 36%, 43% and 86% of gait cycle. The von Mises stress distribution of the prosthesis was calculated. Stress concentration was ascertained and the difference of stress distribution between reconstruction with and without pubic connection plate was analyzed. The displacement and stress peak value of iliac fixation part under the four points of gait cycle were recorded; Comparison of stress on the four transverse iliac fixation screws was studied and the effect of pubic connection plate ascertained.

RESULTS

During the gait cycle, both the stress peak and maximum displacement occurred in the single-leg stance phase, according to 17%-36% of gait cycle. More rational stress distribution could be achieved under the reconstruction with pubic connection plate at 17% and 86% of gait cycle, representing ipsilateral and contralateral single-leg stance respectively, resulting in more even distribution. The maximum stresses of the iliac fixation part were 148.5 MPa and 270.1 MPa under the reconstruction with and without pubic connection plate, with significant difference (P=0.04); The mean displacements of the iliac fixation part were 9.3 mm and 11.7 mm with and without pubic connection plate reconstruction (P=0.03). The average stress level of iliac fixation part could be decreased to 50% and 24% for the iliac fixation screws. However, no micromotions were decreased under the reconstruction with pubic connection plate. Also no significant difference was observed for the relative shift of the iliac fixation part with and without pubic connection plate (P=0.41).

CONCLUSION

The stability of the implant could satisfy the normal walk activity. The pubic connection plate played an important role in the stability of the endoprosthesis, decreasing the stress peak and elongation of the durability.

Age, gender, and race/ethnic differences in total body and subregional bone density

SUMMARY

Total body bone density of adults from National Health and Nutrition Examination Survey (NHANES) 1999-2004 differed as expected for some groups (men>women and blacks>whites) but not others (whites>Mexican Americans). Cross-sectional age patterns in bone mineral density (BMD) of older adults differed at skeletal sites that varied by degree of weight-bearing.

INTRODUCTION

Total body dual-energy X-ray absorptiometry (DXA) data offer the opportunity to compare bone density of demographic groups across the entire skeleton.

METHODS

The present study uses total body DXA data (Hologic QDR 4500A, Hologic, Bedford MA, USA) from the NHANES 1999-2004 to examine BMD of the total body and selected skeletal subregions in a wide age range of adult men and women from three race/ethnic groups. Total body, lumbar spine, pelvis, right leg, and left arm BMD and lean mass from 13,091 adults aged 20 years and older were used. The subregions were chosen to represent sites with different degrees of weight-bearing.

RESULTS

Mean BMD varied in expected ways for some demographic characteristics (men>women and non-Hispanic blacks>non-Hispanic whites) but not others (non-Hispanic whites>Mexican Americans). Differences in age patterns in BMD also emerged for some characteristics (sex) but not others (race/ethnicity). Differences in cross-sectional age patterns in BMD and lean mass by degree of weight-bearing in older adults were observed for the pelvis, leg, and arm.

CONCLUSION

This information may be useful for generating hypotheses about age, race, and sex differences in fracture risk in the population.

The decline in hip bone density after gastric bypass surgery is associated with extent of weight loss

CONTEXT

Bariatric surgery is common and may be associated with deleterious effects on the skeleton.

OBJECTIVE

Our objective was to assess bone metabolism and bone mineral density (BMD) after Roux-en-Y gastric bypass.

DESIGN AND SETTING

We conducted a 1-yr prospective longitudinal study at a university hospital bariatric surgery practice and metabolic bone disease unit.

PARTICIPANTS

Participants included 23 obese (mean body mass index 47 kg/m(2)) men and women, aged 20-64 yr.

MAIN OUTCOME MEASURES

Serum PTH, 25-hydroxyvitamin D, osteocalcin, and urinary N-telopeptide, and BMD were assessed.

RESULTS

Patients lost 45 +/- 2 kg 1 yr postoperatively (P < 0.01). PTH increased early (3 months, 43-50 pg/ml; P < 0.001) and urinary calcium dropped (161-92 mg/24 h; P < 0.01), despite doubling of calcium intake (1318-2488 mg/d; P < 0.001). Serum 25-hydroxyvitamin D concentrations were unchanged (23-26 ng/ml), although vitamin D intake increased by 260% (658 IU/d at baseline to 1698 IU/d at 12 months; P < 0.05). Markers of bone remodeling rose (P < 0.01 for both urinary N-telopeptide and osteocalcin), whereas BMD decreased at the femoral neck (9.2%, P < 0.005) and at the total hip (8.0%, P < 0.005). These declines were strongly associated with the extent of weight loss (femoral neck: r = 0.90, P < 0.0001; and total hip: r = 0.65, P = 0.02). Lumbar spine and distal radius sites did not change.

CONCLUSIONS

After Roux-en-Y gastric bypass, there was evidence of calcium and vitamin D malabsorption. Bone turnover increased, and hip bone density rapidly declined. The decline in hip BMD was strongly associated with weight loss itself. Vigilance for nutritional deficiencies and bone loss in patients both before and after bariatric surgery is crucial.

[Effect of the diet with different microelement composition on the state of alveolar and pelvic bones in rats]

During this experimental study with 6 week-old rats the rate of alveolar bone resorption increased with the balanced diet and drinking water containing 50 mg/l NaF, which is similar to the group of rats observed in case of periodontitis model with the same diet and supplemented with ammonium chloride 5 mg/kg. The mineral complex (Mg-sulfat, Zn-sulfat, Mr-sulfat, Na-citrat) 300 mg/kg possessing a pronounced anti acidosis effect when added to the same balanced diet and sodium fluoride in drinking water with the same concentration prevents resorption processes in the alveolar bone and reduces toxicity action of fluorides on the alveolar and pelvic bones by decreasing metabolic acidosis in the bone tissue.

[Biomechanics of pelvic ring and its structural elements]

Calculations and diagrams of the force distribution in pelvic bones' zone are presented. In persons without injuries and skeletal abnormalities all forces functioning on the pelvic ring are shown to be in balance. Proposed method of calculations enables to detect the treatment tactics (either conservative or operative management) in patients with pelvic bone fractures as well as in congenital abnormalities.

Running in ostriches (Struthio camelus): three-dimensional joint axes alignment and joint kinematics

Although locomotor kinematics in walking and running birds have been examined in studies exploring many biological aspects of bipedalism, these studies have been largely limited to two-dimensional analyses. Incorporating a five-segment, 17 degree-of-freedom (d.f.) kinematic model of the ostrich hind limb developed from anatomical specimens, we quantified the three-dimensional(3-D) joint axis alignment and joint kinematics during running (at ∼3.3 m s–1) in the largest avian biped, the ostrich. Our analysis revealed that the majority of the segment motion during running in the ostrich occurs in flexion/extension. Importantly, however, the alignment of the average flexion/extension helical axes of the knee and ankle are rotated externally to the direction of travel (37° and 21°, respectively) so that pure flexion and extension at the knee will act to adduct and adbuct the tibiotarsus relative to the plane of movement, and pure flexion and extension at the ankle will act to abduct and adduct the tarsometatarsus relative to the plane of movement. This feature of the limb anatomy appears to provide the major lateral (non-sagittal) displacement of the lower limb necessary for steering the swinging limb clear of the stance limb and replaces what would otherwise require greater adduction/abduction and/or internal/external rotation, allowing for less complex joints, musculoskeletal geometry and neuromuscular control. Significant rotation about the joints'non-flexion/extension axes nevertheless occurs over the running stride. In particular, hip abduction and knee internal/external and varus/valgus motion may further facilitate limb clearance during the swing phase, and substantial non-flexion/extension movement at the knee is also observed during stance. Measurement of 3-D segment and joint motion in birds will be aided by the use of functionally determined axes of rotation rather than assumed axes, proving important when interpreting the biomechanics and motor control of avian bipedalism.

[Von Mises stresses research of three-fin acetabular components and pelvis bone with segmental bone defect of acetabulum using rosette strain gages method]

OBJECTIVE

To set up the experimemtal model with superior segmental bone defect in acetabulum and implant the three-fin acetabular component, and examine the Von Mises stresses of pelvis bone with simulating single leg position in vitro using rosette strain gages method (RSGD).

METHODS

Four kinds of three-fin components were made based on measurement of diameter, depth and roof thickness of acetabular specimens. These kinds of three-fin acetabular components based on spreaded degrees of lateral fins (0, 36.45 and 60 degrees). The superior segmental bone defect of acetabulum in 4 cadaver pelvis specimens was made,then simulated the actual position to place implant into acetabular bone. A blank control group was set up. After being fit up the 7 sets of rosette strain gages,then specimen to test the pelvic Von Mises stresses simulating the static load of single leg on the mechanic machine. Progressive load was graded into 150, 300, 450, 600, 750 and 900 N. We obtained the strains informations about loaded and un-loaded pelvis bone.

RESULTS

Based on computed the strains informations,we were informed the Von Mises stresses about pelvis bone. The maximal Von Mises stresses of selected local position was 6.93 MPa and the minimal Von Mises stresses of selected local position was 1.08 MPa.

CONCLUSION

Providing the data about the main part of three-fin acetabular component to optimize spreaded degrees of lateral fins.

Age-related trends in hip geometry in Sri Lankan women: a cross-sectional study

Indices of hip geometry are known to be predictive of hip fractures while sex and ethnic differences in hip geometry have been previously demonstrated. Age-related trends in hip geometry among Asians, however, have not been studied sufficiently. A total of 280 healthy, perimenopausal women, aged between 32 and 97 years, were selected from the Community Study Area of the Faculty of Medicine, Galle, Sri Lanka. Hip DXA images were analyzed further to calculate the hip axis length, neck-shaft angle, and femoral neck width at the narrowest point of the femoral neck. Standard formulae were used to calculate cross-sectional area, cross-sectional moment of inertia, and section modulus in the femoral neck region. Mean (SD) age, weight, height, femoral neck bone mineral density (BMD), hip axis length, neck-shaft angle, neck width, cross-sectional area, and cross-sectional moment of inertia of the study sample were 56.8 (13.0) years, 47.8 (10.1) kg, 1.48 (0.06) m, 0.704 (0.147) g/cm(2), 90.6 (5.6) mm, 123.2 (5.7) degrees, 2.99 (0.24) cm, 2.00 (0.42) cm(2), and 1.62 (0.47) cm(4), respectively. Height and weight of subjects had positive correlations with most of the indices of hip geometry. Femoral neck BMD, cross-sectional area and section modulus showed a rapid reduction during the postmenopausal period. With advancing age, there was a marginal but statistically nonsignificant expansion of the neck width, increase in the hip axis length, and narrowing of the neck-shaft angle. In conclusion, this study demonstrated a gradual loss of BMD in postmenopausal age, accompanied by thinning of the cortical shell and deterioration of the resistance to bending in the femoral neck of this group of healthy women. The clinical relevance of the marginal changes seen in other indices such as neck-shaft angle, hip axis length, and neck width is not known.

The use of sparse CT datasets for auto-generating accurate FE models of the femur and pelvis

The finite element (FE) method when coupled with computed tomography (CT) is a powerful tool in orthopaedic biomechanics. However, substantial data is required for patient-specific modelling. Here we present a new method for generating a FE model with a minimum amount of patient data. Our method uses high order cubic Hermite basis functions for mesh generation and least-square fits the mesh to the dataset. We have tested our method on seven patient data sets obtained from CT assisted osteodensitometry of the proximal femur. Using only 12 CT slices we generated smooth and accurate meshes of the proximal femur with a geometric root mean square (RMS) error of less than 1 mm and peak errors less than 8 mm. To model the complex geometry of the pelvis we developed a hybrid method which supplements sparse patient data with data from the visible human data set. We tested this method on three patient data sets, generating FE meshes of the pelvis using only 10 CT slices with an overall RMS error less than 3 mm. Although we have peak errors about 12 mm in these meshes, they occur relatively far from the region of interest (the acetabulum) and will have minimal effects on the performance of the model. Considering that linear meshes usually require about 70-100 pelvic CT slices (in axial mode) to generate FE models, our method has brought a significant data reduction to the automatic mesh generation step. The method, that is fully automated except for a semi-automatic bone/tissue boundary extraction part, will bring the benefits of FE methods to the clinical environment with much reduced radiation risks and data requirement.

From bone to plausible bipedal locomotion using inverse kinematics

The purpose of this study is to validate a method based on anatomical data and biomechanical locomotor hypotheses that could be applied in palaeontology to simulate locomotion in fossil hominids. The main problem is to ensure that purely mathematical simulation, based on anatomical descriptions, is enough to test hypotheses on human motion control. A 3D geometric model of the lower limb was therefore processed from anatomical descriptions. From this 3D model, we developed a method to retrieve natural lower-limb motion depending on chosen constraints. We assumed that the role of lower-limb motion is to make the feet move from one footprint to the next by following a trajectory that resembles that of living humans (primary task). This method based on inverse kinematics also allows biomechanical laws of bipedal locomotion to be taken into account (secondary tasks). The laws tested in this study relate to preserving joint limits, minimizing energy and minimizing the distance to a rest posture proposed by anthropologists and viewed as input to our system. A weighted sum of the resulting derivable cost functions enabled us to select a specific solution in the null space of the primary task. In order to validate this approach, we compared simulated and captured motion from ten subjects for whom anthropometrical data were recorded. We concluded that this "anatomically based bipedalism simulation" seems promising as a means of investigating natural locomotion behaviour and might also be used to retrieve natural locomotion in fossil hominids where only little knowledge is available.

Skeletal muscle mass, fat mass, and hip bone mineral density in elderly women with hip fracture

Soft tissue body composition strongly affects bone health. Our aim was to investigate the relationship between both skeletal muscle mass (SMM) and fat mass (FM) and femoral bone mineral density (BMD) in a sample of elderly women with hip fracture. We assessed 293 of 325 hip fracture women admitted consecutively to a rehabilitation hospital. Soft tissue body composition and BMD were assessed by dual-energy X-ray absorptiometry (DXA), 23.2 +/- 7.7 (mean +/- SD) days after fracture occurrence. BMD was measured at four sites (neck, total femur, trochanter, intertrochanteric area) in the unfractured femur. Appendicular lean mass (aLM) was calculated as the sum of LM in arms and legs. We used two approaches to adjust aLM for body size: aLM divided by height squared (aLM/ht(2)), and aLM adjusted for height and FM (residuals). Both FM and aLM were significantly correlated with femoral BMD. However, the correlation coefficients for aLM were lower than for FM; they further decreased after adjustment for height squared, and were no longer significant after correction for both height and FM (residuals). When FM, aLM/ht(2), age, and time spent between fracture occurrence and DXA assessment were included together as the independent variables in a regression model, FM was the only independent variable significantly associated with BMD. The coefficients of partial correlation ranged from 0.414 to 0.647 depending on the femoral region of BMD assessment (P < 0.001). FM, but not SMM emerged as a pivotal determinant of BMD in our sample of hip fracture women.

Bone density and bone area in Canadian Aboriginal women: the First Nations Bone Health Study

INTRODUCTION

Canadian Aboriginal women are at increased risk of fracture compared with the general population.

HYPOTHESIS

There is disproportionately reduced bone density in Aboriginal women as compared to white females of similar age.

METHODS

A random age-stratified (25-39, 40-59 and 60-75) sample of Aboriginal women (n=258) and white women (n=181) was recruited. All subjects had calcaneus and distal forearm bone density measurements, and urban participants (n=397 [90.4%]) also had measurements of the lumbar spine, hip and total body.

RESULTS

Unadjusted measurements were similar in the two groups apart from the distal forearm which showed a significantly lower mean Z-score in the Aboriginal women (p=0.03). Aboriginal women were heavier than white women (81.0+/-18.0 kg vs. 76.0+/-18.0 kg, p=0.02). Weight was directly associated with BMD at all measurement sites (p<0.00001) and potentially confounded the assessment of ethnicity on bone mass measurements. Weight-adjusted ANCOVA models demonstrated significantly lower bone density in Aboriginal than white women for the calcaneus, distal forearm, and total body (all p<0.05), but not at the other sites. ANCOVA models (adjusted for age, height and weight) were used to explore differences in bone area and bone mineral content (BMC). There was a significant effect of ethnicity on bone area with Aboriginal women having larger adjusted mean values than white women (lumbar spine p=0.038, total hip p=0.0004, total body p=0.020). In contrast, there was no detectable effect of ethnicity on BMC (all p>0.2).

CONCLUSIONS

We identified significant site-specific differences in age-and weight-adjusted bone density for Aboriginal and white women. Larger bone area, rather than a reduction in BMC, appeared to be primarily responsible. Further work is needed to define how these differences in bone density and geometry affect indices of bone strength.

Serum 25-hydroxyvitamin D, parathyroid hormone, and bone mineral density in men: the Rancho Bernardo study

INTRODUCTION

This study examined the distribution and determinants of serum 25-hydroxyvitamin D (25OHD) and parathyroid hormone (PTH) and their associations with bone mineral density (BMD) at the hip and spine in 414 older men (mean age 74 years) living in southern California.

METHODS

At a clinic visit (1997-2000), demographic and lifestyle information, fracture history, and medication use were recorded; venous blood for serum 25OHD and PTH was obtained; and BMD was measured at the hip and spine.

RESULTS

Only one man had vitamin D deficiency (25OHD <20 nmol/l), but 15.5% of the men had high parathyroid levels (PTH >or=65 pg/ml). The mean 25OHD and PTH levels were 109.0 nmol/l and 50.3 pg/ml, respectively. Overall, 21.5% used calcium and 9.7% used vitamin D supplements. Serum 25OHD decreased with age and was lowest in the winter; levels were higher in supplement users (vitamin D and/or calcium; p<0.01). Serum PTH did not vary by age or season, and it was lower in supplement users (p<0.01). After excluding 12 men who were outliers for serum 25OHD and PTH, there was no significant correlation between serum 25OHD and PTH (r=-0.05, p=0.3). In multiple adjusted models, serum 25OHD was positively associated with BMD at the hip (p=0.01) and spine (p=0.001). Serum PTH was moderately and inversely associated with BMD at the hip (p=0.04) but not at the spine (p=0.77).

CONCLUSION

We conclude that serum 25OHD is associated with bone health in older, community-dwelling men.

Finite element modelling of the pelvis: inclusion of muscular and ligamentous boundary conditions

Previous finite element studies of the pelvis, including subject-specific studies have made extensive simplifications with regards to the boundary conditions used during analysis. Fixed boundary conditions are generally utilised at the pubis and superior part of the ilium. While it can be demonstrated that these models provide a close match for certain in vitro experiments that use similar boundary conditions, the resulting stress-strain fields in the cortex in particular are unlikely to be those found in vivo. This study presents a finite element analysis in which the pelvis is supported by muscular and ligamentous boundary conditions, applied using spring elements distributed over realistic attachment sites. The analysis is compared to an analysis in which the pelvis is restrained by fixed boundary conditions applied at the sacro-iliac joints. Striking differences in the stress-strain fields observed in cortical bone in particular, are found between the two analyses. The inclusion of muscular and ligamentous boundary conditions is found to lower the occurrence of stress concentrations within the cortex.

Prediction of the Modal Characteristics of the Human Spine at Resonant Frequency Using Finite Element Models

To understand the dynamic characteristics of the human spine, a detailed three-dimensional finite element model of the lower thorax to pelvis segment, T12-pelvis, was developed based on actual vertebral geometry. After modal analysis, the resonant frequencies of different spinal segments were obtained. The vibration mode of T12-pelvis shows that the human upper body mainly performs the vertical motion during whole-body vibration and the lumbar spine segment conducts translation and rotation in the sagittal plane. The lower segments of the lumbar spine move in flexion and the upper lumbar segments move in extension. This investigation may be helpful in understanding further the biomechanical behaviour of the human spine under the condition of whole-body vibration and to offer potential references for spinal disease treatments and product design in industry.

Effects of pelvic skeletal asymmetry on trunk movement: three-dimensional analysis in healthy individuals versus patients with mechanical low back pain

STUDY DESIGN

Comparative analysis and correlational research design were used to investigate the association between anthropometry and biomechanical performance among asymptomatic subjects and patients with low back pain (LBP).

OBJECTIVES

To examine the association between pelvic asymmetry and patterns of trunk motion in asymptomatic and LBP subjects. Secondary objective was to investigate the association between restricted trunk motion, laterality of referred pain, and pelvic asymmetry.

SUMMARY OF BACKGROUND DATA

Subtle pelvic asymmetry (exhibited as either lateral pelvic tilt or iliac rotational asymmetry), which is common among normal individuals, has not been convincingly linked to abnormalities in back movements. Given the difficulty in diagnosing most LBP, a classification using pelvic asymmetry and patterns of movement could be helpful in establishing a rational treatment plan.

METHODS

Fifty-nine subjects with no history of LBP and 54 patients with mechanical unilateral LBP were tested. An anthropometric frame was used to measure pelvic asymmetry in standing. Dynamic motion data, comprised of the principal and coupled movements, were collected using the Qualysis Motion Capture System.

RESULTS

While the groups did not differ in the total range of lumbar movement, the LBP group exhibited significantly higher asymmetry in the principal motion. The groups differed significantly in the pattern of coupled rotation during lateral flexion. Asymmetry in lumbar lateral flexion was highly related to two types of pelvic asymmetry: lateral pelvic tilt (LPT) and iliac rotation asymmetry (IRA). Asymmetry in lumbar axial rotation was highly related to IRA but weakly related to LPT.

CONCLUSIONS

This study demonstrates objective differences in patterns of lumbar movement between asymptomatic subjects and patients with LBP. The study also demonstrates that subtle anatomic abnormality in the pelvis is associated with altered mechanics in the lumbar spine. We suggest that asymmetry of lumbar movement may be a better indicator of functional deficit than the absolute range of movement in LBP.

Double-step registration of in vivo stereophotogrammetry with both in vitro 6-DOFs electrogoniometry and CT medical imaging

Standard registration techniques of bone morphology to motion analysis data often lead to unsatisfactory motion simulation because of discrepancies during the location of anatomical landmarks in the datasets. This paper describes an iterative registration method of a three-dimensional (3D) skeletal model with both 6 degrees-of-freedom joint kinematics and standard motion analysis data. The method is demonstrated in this paper on the lower limb. The method includes two steps. A primary registration allowed synchronization of in vitro kinematics of the knee and ankle joints using flexion/extension angles from in vivo gait analysis. Results from primary registration were then improved by a so-called advanced registration, which integrated external constraints obtained from experimental gait pre-knowledge. One cadaver specimen was analyzed to obtain both joint kinematics of knee and ankle joints using 3D electrogoniometry, and 3D bone morphology from medical imaging data. These data were registered with motion analysis data from a volunteer during the execution of locomotor tasks. Computer graphics output was implemented to visualize the results for a motion of sitting on a chair. Final registration results allowed the observation of both in vivo motion data and joint kinematics from the synchronized specimen data. The method improved interpretation of gait analysis data, thanks to the combination of realistic 3D bone models and joint mechanism. This method should be of interest both for research in gait analysis and medical education. Validation of the overall method was performed using RMS of the differences between bone poses estimated after registration and original data from motion analysis.

The frontal pelvic plane provides a valid reference system for implantation of the acetabular cup: spatial orientation of the pelvis in different positions

BACKGROUND

The frontal pelvic plane has traditionally served as the reference plane for implantation of the acetabular cup during total hip arthroplasty, with referencing performed with the patient supine on the operating table. During daily activities in an upright position, the frontal pelvic plane changes from a horizontal to a vertical orientation. If this change in orientation is accompanied by a substantial change in pelvic inclination angle, it would mean that the use of the frontal pelvic plane as a reference plane for implantation of the acetabular cup would not be valid for proper alignment of the cup. To evaluate this possibility, we measured the change of inclination of the pelvis from the supine to the standing position.

SUBJECTS AND METHODS

We evaluated 120 patients, first positioned in a standing position and then supine on a table. Three pelvic landmarks were digitized percutaneously, and the spatial coordinates were calculated with regard to pelvic orientation in the horizontal and the vertical plane.

RESULTS

We found a mean inclination of 6.7 degrees in the standing position and 5.6 degrees in the supine position. Patients who were more than 60 years of age who did not have coxarthrosis had a greater inclination angle (8.7 degrees ) while standing. Pelvic orientation was stable with regard to the supine and standing positions. These results were independent of sex, level of arthrosis, or status after implantation of a total hip replacement.

INTERPRETATION

The frontal pelvic plane is a valid reference plane for implantation of the acetabular cup.

Sagittal spinopelvic balance in normal children and adolescents

The sagittal spinopelvic balance is poorly documented in normal pediatric subjects. The purpose of this study is to characterize the sagittal spinopelvic balance in the pediatric population and to evaluate the correlations between spinopelvic parameters. Seven parameters were evaluated from the lateral standing radiographs of 341 normal subjects aged 3-18 years old: thoracic kyphosis (TK), thoracic tilt (TT), lumbar lordosis (LL), lumbar tilt (LT), sacral slope (SS), pelvic tilt (PT) and pelvic incidence (PI). The mean values for the pelvic parameters were 49.1+/-11.0, 7.7+/-8.0 and 41.4+/-8.2 degrees for PI, PT and SS, respectively. The mean values for the spinal parameters were 48.0+/-11.7, 44.0+/-10.9, -7.3+/-5.2 and -3.1+/-5.2 degrees for LL, TK, LT and TT, respectively. The spinopelvic parameters were different from those reported in normal adults, but the correlations between the parameters were similar. PI was significantly related to SS and PT. Significant correlations were found between the parameters of adjacent anatomical regions. Pelvic morphology (PI) regulates sagittal sacro-pelvic orientation (SS and PT). Sacral orientation (SS) is correlated with the shape (LL) and orientation (LT) of the lumbar spine. Adjacent anatomical regions of the spine and pelvis are interdependent, and their relationships result in a stable and compensated posture, presumably to minimize energy expenditure. Results from this study could be used as an aid for the planning of surgery in pediatric patients with spinal deformity in order to restore a relatively normal sagittal spinopelvic balance.

[Reactions of the human bone system in space flight: phenomenology]

Results of multi-year bone observations in crewmembers of long-term (6 to 14 mos.) Salyut and Mir missions have been summarized. The theoretical expectation of bone losses (mineral bone density, MBD) was consistent only in the trabecular of the lower skeleton (lumbar spine, femur proximal epiphysis, pelvis). The upper skeleton bones (skull, cervical spine) demonstrated a clears-defined trend toward an increase in mineral content. There is a direct dependence of MBD losses on a skeleton bone position relative to the gravity vector and bone structure. Post-flight MBD did not, as a rule, deviate from the WHO-defined limits (T-criterion); in several instances MBD loss was qualified as local osteopenia. Shifts in MBD, same as MBD recovery rate, vary with subjects and, therefore, deny their dependence on flight duration. By and large, MBD shifts are interpreted as a functional adaptation of bone tissue to changing mechanic demands.